Year	U.S. dollars (Units)
1980	334.430
1981	330.808
1982	268.415
1983	289.889
1984	265.387
1985	207.228
1986	232.527
1987	290.681
1988	323.516
1989	329.019
1990	391.983
1991	452.080
1992	505.038
1993	494.606
1994	512.036
1995	549.606
1996	524.624
1997	551.041
1998	508.557
1999	501.750
2000	493.333
2001	414.027
2002	457.662
2003	670.897
2004	852.696
2005	922.416
2006	916.563
2007	930.798
2008	868.532
2009	1011.420
2010	1222.197
2011	1324.607
2012	1261.443
2013	1191.994
2014	1250.627
2015	1104.543
2016	1099.146
2017	1199.628
2018	1215.317
2019	1134.400
2020	1014.795
2021	1162.787
2022	1100.982
2023	1052.122
2024	1107.084
2025	1152.451
2026	1191.061
2027	1219.862
2028	1249.710
2029	1321.604